Staging fuel nozzle

Abstract

A main swirler of a triple annular configuration that is partitioned by a pre-filmer and a separator is installed in an inlet port of a main air flow channel. The vicinity of the inner wall of the main air flow channel provided with a main fuel injection port is bulged radially outward from the innermost surface (innermost surface of a small swirler) of a main swirler. Further, a distance from the main fuel injection port and the pre-filmer is set such that an effective opening area between the pre-filmer and “the inner wall of the main air flow channel provided with the main fuel injection port” is equal to an effective opening area of the small swirler. The swirling directions of the swirlers of the main swirler are “clockwise”-“counter-clockwise”-“clockwise” respectively along the radial outward direction when the swirling direction of the innermost swirler is taken as “clockwise”.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to a staging fuel nozzle of a gas turbine engine, and more particularly to a staging fuel nozzle that further increases combustion efficiency in a low or medium load mode of the engine and contributes to further reduction in NOx in a medium or high load mode of the engine.[0003]2. Description of Related Art[0004]A rich-lean combustion system based on diffusion combustion has been used in combustors of conventional jet engines for aircrafts. With such a combustion system, the correlation between the equivalent ratio φ and NOx generation amount has an almost symmetrical convex curved distribution with a center close to φ=1. Therefore, by conducting combustion in a rich state (fuel-rich state) with φ>1 in the upstream portion inside the combustor and then introducing air, it is possible to include combustion in a lean state (fuel-lean state) with φ<1 and avoid the combustion in the vicin...

AI Technical Summary

Benefits of technology

[0008]However, since the amount of air for improving the atomization of fuel is less than the total amount of air passing through the main air flow channel, the effect thereof is small. Further, since a fuel-rich zone appears on the inside in the radial direction of the annular outlet of the main air flow channel, NOx can be easily generated.

[0029]In order to reduce the amount of NOx generated from the main flame, it is important to atomize the fuel and mix the fuel homogeneously with air. In a fuel nozzle of a pre-filming type, fuel jet collides with a cylinder (liquid film forming body) and forms a fuel film on the inner surface of the cylinder, and the fuel atomization is conducted by the inner and outer air flows at the downstream end of the cylinder. In such a fuel nozzle, in order to attain a high degree of atomization, it is necessary that the fuel jet is caused to reach the cylinder reliably even when the amount of fuel is small and the air flow has a high speed at the downstream end of the cylinder. In accordance with the present invention, the inner wall surface of the main air flow channel where the fuel injection port is provided bulges radially outward from the innermost sluice of the swirler located on the upstream side. Therefore, the fuel jet can reliably reach the cylinder and the air flow speed can be increased. Further, because the triple annular swirler in accordance with the present invention is used, fuel atomization is enhanced by shear action of adjacent swirling flows, air and fuel are mixed more homogeneously, and the amount of NOx in the combustion gas can be further reduced. In addition, the backward-facing step flame stabilizer located between the pilot air flow channel and main air flow channel demonstrates an effect of forming a stable main flame by reliably bringing the pilot flame or high-temperature burned gas produced in the pilot region into contact with the main per-mixture. Furthermore, since the film-shaped air jetting port is provided in the inner wall surface of the outlet of the main air flow channel, the fuel that has adhered to the inner wall surface of the main air flow channel is atomized by the air flow jetted out from the air jetting port, mixing of air and fuel is enhanced, combustion efficiency is increased, and contribution is made to reduction in NOx emission.

Problems solved by technology

However, since the amount of air for improving the atomization of fuel is less than the total amount of air passing through the main air flow channel, the effect thereof is small.

As described hereinabove, in all of the above-described staging fuel nozzles, fuel is premixed with a sufficient amount of air and the mixture is subjected to lean combustion in the main burner to prevent the generation of high-temperature flame and reduce the amount of NOx that is generated in a large amount during high-temperature combustion, but these staging fuel nozzles have not yet reached the stage of practical use.

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